CN114478014A - Silicon carbide ceramic material, ceramic mold and preparation method thereof - Google Patents

Abstract

The application discloses silicon carbide ceramic material, ceramic mould and preparation method thereof, and the silicon carbide ceramic material comprises: 75-90% of silicon carbide micro powder, 2-5% of binder and 5-20% of sintering aid; wherein, the corresponding grain diameter is 0.2-1.0 μm when the cumulative grain size distribution percentage of the silicon carbide micro powder reaches 50%. The preparation method of the ceramic mold comprises the following steps: grinding each raw material of the silicon carbide ceramic material according to a preset mass ratio; mixing the ground raw materials to form powder; pre-pressing and molding the powder by using a preset mold to form a blank; and firing the blank to form the ceramic die. By adopting the silicon carbide as the main raw material, the hardness of the silicon carbide is far higher than that of graphite, the wear resistance is good, and meanwhile, the C-Si bond energy of the silicon carbide is larger, so that the silicon carbide is more difficult to oxidize than the graphite under the high-temperature condition, pits generated by oxidation and falling are reduced, the service life of the die is effectively prolonged, and the cost input brought by later maintenance is reduced.

Description

Silicon carbide ceramic material, ceramic mold and preparation method thereof

Technical Field

The application relates to the technical field of molds, in particular to a silicon carbide ceramic material, a ceramic mold and a preparation method thereof.

Background

The 3D glass forming is mainly realized by adopting a hot bending process, cut glass is placed between an upper arc-shaped mould and a lower arc-shaped mould, the glass is softened by sequentially heating to a certain temperature through a plurality of sections of stations in a hot bending machine, the softened glass is gradually attached to the moulds under a certain pressure, and then the softened glass is cooled by pressure maintaining and gradual cooling, so that the 3D glass with the curved surface modeling is obtained. At present, the conventional hot bending die is made of graphite material, the graphite material has the characteristics of high temperature resistance, good heat conductivity, corrosion resistance, low cost and easiness in processing, and the higher the temperature is, the harder the graphite material is, so that the problem of deformation is avoided, and the maximum precision degree can be ensured; meanwhile, the graphite mold is not soaked with glass, so that the surface quality of a glass product can be ensured.

The existing graphite mold has the service life of more than 1000 times for conventional small-angle two-side bent glass products, but the molding of the glass products is more and more complex along with the 3D curved surface, the processing difficulty is correspondingly improved, the requirements on the mold for product molding are also severer, the graphite mold is often used hundreds of times or even dozens of times because the graphite is easy to oxidize, the hardness is low, the graphite mold is not wear-resistant, the serious oxidation powder falling phenomenon is generated, the defects of the surface die mark and the pits of the product are heavier, the mold needs to be maintained and polished in time, and the polishing difficulty and the cost are larger.

Disclosure of Invention

In view of the above, the present application provides a silicon carbide ceramic material and a method for preparing a ceramic mold, so as to solve the problem that the existing graphite mold is easily oxidized at high temperature and is not wear-resistant, which results in an increase in maintenance cost.

In a first aspect of the present application, there is provided a silicon carbide ceramic material comprising:

75-90% of silicon carbide micro powder, 2-5% of binder and 5-20% of sintering aid;

wherein, the corresponding grain diameter is 0.2-1.0 μm when the cumulative grain size distribution percentage of the silicon carbide micro powder reaches 50%.

Optionally, the binder comprises at least one of organic cellulose, epoxy resin or bentonite.

Optionally, the sintering aid includes at least one of aluminum oxide, feldspar powder, silica micropowder, carbon micropowder, boron carbide, absolute ethyl alcohol or titanium diboride.

In a second aspect, a method for preparing a ceramic mold is provided, which includes:

grinding each raw material of the silicon carbide ceramic material according to a preset mass ratio;

mixing the ground raw materials to form powder;

pre-pressing and molding the powder by using a preset mold to form a blank;

and firing the blank to form the ceramic die.

Optionally, the grinding of the silicon carbide ceramic material according to a preset mass ratio includes:

taking the raw materials in a preset mass ratio, and respectively adding the raw materials and silicon carbide grinding balls into a ball mill for ball milling, wherein the weight of the silicon carbide grinding balls is twice of that of the corresponding raw materials.

Optionally, mixing the dry-milled raw materials to form a powder, including:

mixing all the ground raw materials according to the proportion, and adding distilled water or absolute ethyl alcohol, wherein the weight of the distilled water or the absolute ethyl alcohol is equal to the total weight of all the raw materials;

adding silicon carbide grinding balls, and carrying out ball milling on the raw materials by using a planetary ball mill to form slurry, wherein the weight of the silicon carbide grinding balls is twice of the total weight of all the raw materials;

drying the slurry to form powder;

and sieving the powder to form the powder.

Optionally, the ball milling of the raw materials by using a planetary ball mill includes:

the raw materials are ball-milled for 3 to 5 hours in a planetary ball mill at 360 r/min.

Optionally, the drying the slurry includes:

the slurry was placed in an oven and dried at 40-60 ℃ for 2 h.

Optionally, the sieving is performed by using a 60-80 mesh sieve.

Optionally, the powder is pre-pressed and molded by using a preset mold to form a blank, including:

and adding the powder into the die, pressurizing to 50-200MPa through the die, and maintaining the pressure for 60-150s to form the blank.

Optionally, firing the blank to form the ceramic mold includes:

and heating the blank from room temperature to 500 ℃, preserving the heat for 20-40min, then continuously heating to 1300-1600 ℃, and maintaining the pressure for 3h to form the ceramic die.

In a third aspect, a ceramic mold is provided, comprising silicon carbide in a mass proportion of greater than 75%.

According to the preparation method of the silicon carbide ceramic material and the ceramic mold, silicon carbide is used as a main raw material, the hardness of the silicon carbide is far higher than that of graphite, the wear resistance is good, meanwhile, the C-Si bond energy of the silicon carbide is large, and the silicon carbide is more difficult to oxidize than the graphite under the high-temperature condition.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic flow chart of a method for manufacturing a ceramic mold according to an embodiment of the present disclosure;

FIG. 2 is a schematic flow diagram of a mixed feedstock provided in an embodiment of the present application;

fig. 3 is a schematic process flow diagram of a method for manufacturing a ceramic mold according to an embodiment of the present disclosure.

Detailed Description

The technical solutions in the embodiments of the present application are clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. The following embodiments and their technical features may be combined with each other without conflict.

The application provides a silicon carbide ceramic material, including carborundum miropowder, binder and sintering auxiliary agent, be respectively according to the mass ratio: 75-90% of silicon carbide micro powder, 2-5% of binder and 5-20% of sintering aid. Wherein the silicon carbide fine powder has a particle size distribution D50 of 0.2 to 1.0 μm and a purity of 99%, and the particle size distribution D50 represents the particle size corresponding to 50% of the cumulative percentage of particle size distribution of a sample, i.e., 50% of particles having a particle size larger than this value and 50% of particles having a particle size smaller than this value, and D50 is also referred to as the median or median particle size, and for example, when the silicon carbide fine powder has a particle size distribution D50 of 0.2 μm, it represents 50% of particles having a particle size larger than 0.2 μm and 50% of particles having a particle size smaller than 0.2 μm. The particle size distribution of the silicon carbide micro powder directly influences the performance requirements such as density, viscosity and the like of the sintered blank, when the particle size of the micro powder is too large, a good compact blank cannot be obtained within a sintering temperature range, and the defect of micropores in the middle of the blank is easily exposed in the subsequent processing process, so that the surface quality of a die is influenced.

Specifically, a silicon carbide fine powder having the following characteristics was used.

Theoretical physical Properties	SiC
		Molecular weight	40.07
Color state	Colorless, black, greenish black, yellow, etc
		Theoretical density g/cm3	3.16-3.2
Melting Point C	3000
		Boiling point of	3500
Thermal conductivity W/m.k	0.3
		Coefficient of thermal expansion x 10-6/. degree.C	5.2

The binder mainly serves to increase the strength of the green body and does not participate in the sintering reaction. The addition of a proper amount of binder can increase the density of the blank body during the pre-pressing forming, because the binder can increase the plasticity of the silicon carbide powder, reduce the friction force in the particle extrusion process, and enable small particles to be easily filled into gaps of large particles, thereby discharging air holes and increasing the density. The addition amount of the binder is not suitable to be too large, because the binder contains moisture with different proportions, and the moisture is easy to volatilize in the drying process of the green body to cause residual pores in the green body. In some embodiments, the binder includes at least one of organic cellulose, epoxy resin, or bentonite, in other embodiments, the main body of the binder is organic cellulose, and one or more of epoxy resin, bentonite, and the like can be used instead.

The addition of the sintering aid mainly reduces the viscosity of a material system in the sintering process, promotes the flow of a liquid phase, and accelerates the movement of silicon carbide powder and the dissolution and precipitation processes of other oxides, so that the density and the mechanical property of a sintered body are obviously improved; meanwhile, the heat conductivity coefficient of the sintered body can be increased by adding sintering aids such as carbon powder, boron carbide and the like, and the thermal expansion coefficient of the sintered body can be increased by adding aluminum oxide, so that the material is more suitable for being used as a hot bending die. However, the more the sintered materials, the better, the lower the melting point of the sintering aid, the more volatile in the high-temperature sintering process, which is not favorable for improving the density; further, the oxide sintering agent is usually in a liquid phase during sintering, and exists in a grain boundary as a glass phase after sintering, so that the strength is lowered. In some embodiments, the sintering aid comprises at least one of alumina, feldspar powder, silica powder, carbon powder, boron carbide, absolute ethanol, or titanium diboride.

Based on the same inventive concept, the present application also provides a method for preparing a ceramic mold, as shown in fig. 1, comprising:

s10, grinding the raw materials of the silicon carbide ceramic material according to a preset mass ratio;

specifically, the raw materials are taken in a predetermined mass ratio, and the raw material ratio of the silicon carbide ceramic material is as described in any one of the above, for example, 90 kg of silicon carbide fine powder having a particle size D50 of 0.2 μm, 2 kg of organic cellulose (binder) and 8 kg of feldspar powder (sintering aid) are taken, that is, 90%, 2% and 8% by mass, respectively. Adding various raw materials and silicon carbide grinding balls into a ball mill for ball milling, wherein the weight of the added silicon carbide grinding balls is twice of that of the corresponding raw materials, for example, 90 kg of silicon carbide micro powder is added, namely 180 kg of silicon carbide grinding balls are added, 2 kg of organic cellulose is added, 4 kg of silicon carbide grinding balls are added, 8 kg of feldspar powder is added, 16 kg of silicon carbide grinding balls are added, and the ball milling time can be adjusted according to the selected material property and the required particle size, for example, 10 hours, but the method is not limited to the above; when a smaller particle size of the starting material is desired, the time for ball milling may be increased, for example, to 15 hours. Grinding the raw materials respectively to obtain various ground raw materials.

In this example, the mass ratio of the fine silicon carbide powder was 90%, the mass ratio of the binder was 2%, the mass ratio of the sintering aid was 8%, and the particle size distribution D50 of the fine silicon carbide powder was 0.2 μm, and in other embodiments, the mass ratio of the fine silicon carbide powder may be 75%, 78%, 80%, 83%, 85%, 87%, 88%, 90%, or the like; the mass ratio of the binder can be 2.5%, 3%, 4%, 5% and the like; the mass proportion of the sintering aid can be 5%, 7%, 8%, 10%, 12%, 15%, 18%, 20% and the like; the particle size distribution D50 of the fine silicon carbide powder may be 0.2 μm, 0.3 μm, 0.5 μm, 0.7 μm, 0.8 μm, 1.0. mu.m, for example, 87% of the fine silicon carbide powder, 3% of the binder, 10% of the sintering aid, 0.3 μm of the particle size distribution D50 of the fine silicon carbide powder are used.

In the present embodiment, the binder is organic cellulose, the sintering aid is feldspar powder, in other embodiments, the binder may be replaced by at least one of epoxy resin or bentonite, and the sintering aid may be replaced by at least one of aluminum oxide, silicon micropowder, carbon micropowder, boron carbide, absolute ethyl alcohol or titanium diboride.

S20, mixing the ground raw materials to form powder;

in this embodiment, the raw materials are mixed by wet mixing, specifically, all the ground raw materials are added into a planetary ball mill, and distilled water or absolute ethyl alcohol is added, the weight of the distilled water or absolute ethyl alcohol is equal to the total weight of all the raw materials, for example, 90 kg of silicon carbide micro powder, 2 kg of organic cellulose and 8 kg of feldspar powder, the total weight is 100 kg, and then 100 kg of distilled water or absolute ethyl alcohol is added; then adding silicon carbide grinding balls, wherein the weight of the silicon carbide grinding balls is twice of the total weight of all raw materials, for example, 90 kg of silicon carbide micro powder, 2 kg of organic cellulose and 8 kg of feldspar powder, and the total weight is 100 kg, then adding 200 kg of silicon carbide grinding balls; ball-milling and mixing all the raw materials by using a planetary ball mill to form slurry, and then drying and sieving the slurry to obtain powder. In another embodiment, the raw materials may be directly mixed and stirred by a stirrer or the like to sufficiently mix the raw materials.

S30, pre-pressing and forming the powder by using a preset die to form a blank;

in the embodiment, a cold pre-pressing forming mode is adopted, the obtained powder is added into a preset die, the pressure is increased to 50-200MPa through the die, the pressure is maintained for 60-150s, and the powder is formed in the die to form a blank. The preset die is a forming die used for extrusion forming of powder in the field, and the shape of the die can be adjusted according to process requirements, and is not limited herein.

And S40, firing the blank to form the ceramic die.

And putting the blank obtained by pre-pressing into a high-temperature furnace, heating to 500 ℃ from room temperature, preserving heat for 20-40min, then heating to 1300 ℃ and 1600 ℃ for sintering, maintaining the pressure for 3h, and naturally cooling to obtain the ceramic die for hot bending forming. The temperature raising speed can be adjusted according to the actual application scenario, but is not limited herein, for example, the temperature is raised from room temperature to 500 ℃ at a speed of 10 ℃/min for pre-sintering, and the temperature is raised to 1300-1600 ℃ at a speed of 18 ℃/min for sintering after heat preservation. In some embodiments, in order to reduce the cracking of the blank due to the temperature shock, the temperature rise rate can be reduced appropriately; in order to increase the sintering efficiency of the green body, the temperature rise rate can be increased appropriately.

According to the embodiment, by adopting the silicon carbide ceramic material and the preparation method of the ceramic mold, the silicon carbide is adopted as the main raw material, the hardness of the silicon carbide is far higher than that of graphite, the wear resistance is good, meanwhile, the C-Si bond energy of the silicon carbide is larger, and the silicon carbide is more difficult to oxidize than the graphite under the high-temperature condition. In addition, the silicon carbide is sintered in a pressureless mode, and extra pressurization is not needed during firing, so that the sintered ceramic die for hot bending molding has good anisotropic thermal expansion coefficient, and can meet the use requirement at higher temperature.

As shown in fig. 2, in some embodiments, S20, mixing the ground raw materials to form a powder, specifically includes:

s21, mixing all the ground raw materials according to the proportion, and adding distilled water or absolute ethyl alcohol, wherein the weight of the distilled water or the absolute ethyl alcohol is equal to the total weight of all the raw materials;

s22, adding silicon carbide grinding balls, and carrying out ball milling on the raw materials by using a planetary ball mill to form slurry, wherein the weight of the silicon carbide grinding balls is twice of the total weight of all the raw materials;

all the raw materials are added into a planetary ball mill, then distilled water or absolute ethyl alcohol twice the total weight of all the raw materials is added, and silicon carbide grinding balls twice the total weight of all the raw materials are added, and ball milling is carried out for 3-5 hours at 360r/min by using the planetary ball mill, so as to form slurry.

S23, drying the slurry to form powder;

and placing the mixed slurry in an oven to be dried for more than 2 hours at the temperature of 40-60 ℃ so as to remove the distilled water or the absolute ethyl alcohol added during mixing to form powder.

S24, sieving the powder to form the powder;

and (3) loosening and granulating the dried powder by using a 60-80 mesh screen to form powder for prepressing and sintering.

In one embodiment, as shown in fig. 3, the method for preparing the ceramic mold comprises the following steps:

preparing materials: taking the raw materials in a preset mass proportion, and respectively adding the raw materials and silicon carbide grinding balls into a ball mill for ball milling, wherein the weight of the silicon carbide grinding balls is twice of that of the corresponding raw materials;

mixing materials: mixing materials by adopting a wet mixing method, designing a proportion according to a formula, adding distilled water or absolute ethyl alcohol which is equal to the total weight of the raw materials and silicon carbide grinding balls with the weight of 2 times, carrying out ball milling on a planetary ball mill for 3-5h at 360r/min, placing the obtained slurry in an oven, and drying at 40-60 ℃ for about 2h to obtain powder; finally, loosening and granulating by using a 60-80 mesh screen to obtain powder;

pre-pressing and forming: putting the mixed powder into a pre-designed die, pressurizing the powder by the die under the pressure of 50-200MPa, and maintaining the pressure for 60-150s to obtain a blank with a certain bonding force;

and (3) sintering: and (3) placing the blank into a high-temperature furnace, slowly heating the blank to about 500 ℃ from room temperature to prevent cracking caused by sudden temperature change, keeping the temperature at 500 ℃ for 20-40min, heating the blank to 1300-1600 ℃, sintering the blank, and maintaining the pressure for 3h to obtain a compact sintered product.

Based on the same inventive concept, the application also provides a ceramic die for hot bending forming, which comprises silicon carbide, wherein the mass proportion of the silicon carbide in the ceramic die for hot bending forming is more than 75%.

Although the application has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art based upon a reading and understanding of this specification and the annexed drawings. This application is intended to embrace all such modifications and variations and is limited only by the scope of the appended claims. In particular regard to the various functions performed by the above described components, the terms used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary implementations of the specification.

That is, the above description is only an embodiment of the present application, and not intended to limit the scope of the present application, and all equivalent structures or equivalent flow transformations made by using the contents of the specification and the drawings of the present application, such as the combination of technical features between various embodiments, or the direct or indirect application to other related technical fields, are all included in the scope of the present application.

In addition, in the description of the present application, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be considered as limiting the present application. In addition, structural elements having the same or similar characteristics may be identified by the same or different reference numerals. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.

In this application, the word "exemplary" is used to mean "serving as an example, instance, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. The previous description is provided to enable any person skilled in the art to make and use the present application. In the foregoing description, various details have been set forth for the purpose of explanation. It will be apparent to one of ordinary skill in the art that the present application may be practiced without these specific details. In other instances, well-known structures and processes are not shown in detail to avoid obscuring the description of the present application with unnecessary detail. Thus, the present application is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

Claims (12)

1. A silicon carbide ceramic material, comprising:

75-90% of silicon carbide micro powder, 2-5% of binder and 5-20% of sintering aid;

wherein, the corresponding grain diameter is 0.2-1.0 μm when the cumulative grain size distribution percentage of the silicon carbide micro powder reaches 50%.

2. The silicon carbide ceramic material of claim 1, wherein the binder comprises at least one of an organic cellulose, an epoxy, or bentonite.

3. The silicon carbide ceramic material of claim 1, wherein the sintering aid comprises at least one of alumina, feldspar powder, silica micropowder, carbon micropowder, boron carbide, absolute ethyl alcohol, or titanium diboride.

4. A method for preparing a ceramic mold, comprising:

grinding the raw materials of the silicon carbide ceramic material as claimed in any one of claims 1 to 3 in a predetermined mass ratio;

mixing the ground raw materials to form powder;

pre-pressing and molding the powder by using a preset mold to form a blank;

and firing the blank to form the ceramic die.

5. The preparation method according to claim 4, wherein the grinding of the silicon carbide ceramic material according to the preset mass ratio comprises:

taking the raw materials in a preset mass ratio, and respectively adding the raw materials and silicon carbide grinding balls into a ball mill for ball milling, wherein the weight of the silicon carbide grinding balls is twice of that of the corresponding raw materials.

6. The method of claim 4, wherein said mixing said dry-milled feedstock to form a powder comprises:

mixing all the ground raw materials according to the proportion, and adding distilled water or absolute ethyl alcohol, wherein the weight of the distilled water or the absolute ethyl alcohol is equal to the total weight of all the raw materials;

adding silicon carbide grinding balls, and carrying out ball milling on the raw materials by using a planetary ball mill to form slurry, wherein the weight of the silicon carbide grinding balls is twice of the total weight of all the raw materials;

drying the slurry to form powder;

and sieving the powder to form the powder.

7. The method of claim 6, wherein the ball milling the feedstock with a planetary ball mill comprises:

the raw materials are ball-milled for 3 to 5 hours in a planetary ball mill at 360 r/min.

8. The method of claim 6, wherein said drying the slurry comprises:

the slurry was placed in an oven and dried at 40-60 ℃ for 2 h.

9. The method of claim 6, wherein the screening is performed with a 60-80 mesh screen.

10. The preparation method according to claim 4, wherein the pre-pressing the powder material by using a predetermined mold to form a blank comprises:

and adding the powder into the die, pressurizing to 50-200MPa through the die, and maintaining the pressure for 60-150s to form the blank.

11. The method of claim 4, wherein firing the blank to form the ceramic mold comprises:

and heating the blank from room temperature to 500 ℃, preserving the heat for 20-40min, then continuously heating to 1300-1600 ℃, and maintaining the pressure for 3h to form the ceramic die.

12. The ceramic mold is characterized by comprising silicon carbide, wherein the mass ratio of the silicon carbide is more than 75%.

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